This disclosure relates to a method of steering a mining machine cutter in which the mining machine is of the kind having a body arranged to be progressed along a mineral face being cut, the body having at either end a ranging arm pivotally mounted on the body and each arm carrying a rotatable cutting drum. This kind of machine is known as a double-ended ranging drum shearer.
Many means of cutting and extracting wanted mineral are known, but one commonly used form, particularly for winning coal, is to use a ranging drum machine having ranging arms at either end, where a cutting drum having a plurality of cutting picks is rotated at the end of each ranging arm, which is pivotally secured to the body of a machine. The body of the machine is moved along a face, and each rotating drum cuts material from the face.
This type of machine is steered to enable the drum always to cut within the mine face seam by adjusting the pivotal control of the ranging arms. Skilled operators who watch the progress of the drum and the seam can do this manually, but automatic means can also be used since the creation of dust and water sprays can impair the vision of the drum by the operators.
Such a machine carries a plurality of sensors mounted on the machine, the sensors being adapted to measure different parameters of the mining operation and to generate electrical signals representative of said parameters. For example, some of the sensors may be arranged to measure along the face, the pitch or roll of the machine, other sensors may be arranged to measure the movement and direction of the machine, and still other of the sensors may be arranged to measure the positions of the leading and trailing ranging arms with respect to the machine. When steering the cutting machine, it is important to make sure the machine does not wander into strata on either side of the mine face seam. In order to do this, it is normal to leave a few inches of the material being cut to form a roof and floor so that any minor variations in the path of the cutting machine only varies the thickness of the roof and floor left and does not cut into the adjoining strata.
The gate ends of a longwall face are typically higher above the mine floor than the rest of the mine face, for the conveyor bed must go up over the conveyor drives at the gate ends of the mine face. This results in the shearer being raised up at the gate ends. As a result, the shearer operator must pivot the ranging arm lower at the gate ends in order to still effectively mine the coal from the mine face.
A problem can arise where an operator leaves the ranging arm in the lowered position, and attempts to leave the gate end area. If this happens, then the ranging arm is below the undercut limit, and the cutting machine may cut into the mine floor, resulting in possible damage to the machine.